diff --git a/AMSS_NCKU_source/fdderivs_c.C b/AMSS_NCKU_source/fdderivs_c.C
index cd65ac3..5cc52d4 100644
--- a/AMSS_NCKU_source/fdderivs_c.C
+++ b/AMSS_NCKU_source/fdderivs_c.C
@@ -73,6 +73,10 @@ void fdderivs(const int ex[3],
 
     /* 输出清零：fxx,fyy,fzz,fxy,fxz,fyz = 0 */
     const size_t all = (size_t)ex1 * (size_t)ex2 * (size_t)ex3;
+    for (size_t p = 0; p < all; ++p) {
+        fxx[p] = ZEO; fyy[p] = ZEO; fzz[p] = ZEO;
+        fxy[p] = ZEO; fxz[p] = ZEO; fyz[p] = ZEO;
+    }
 
     /*
      * Fortran:
diff --git a/AMSS_NCKU_source/fderivs_c.C b/AMSS_NCKU_source/fderivs_c.C
index 0637cba..5f6b94c 100644
--- a/AMSS_NCKU_source/fderivs_c.C
+++ b/AMSS_NCKU_source/fderivs_c.C
@@ -74,6 +74,11 @@ void fderivs(const int ex[3],
 
     // fx = fy = fz = 0
     const size_t all = (size_t)ex1 * (size_t)ex2 * (size_t)ex3;
+    for (size_t p = 0; p < all; ++p) {
+        fx[p] = ZEO;
+        fy[p] = ZEO;
+        fz[p] = ZEO;
+    }
 
     /*
      * Fortran loops: